Diazotype developer composition containing a potassium borate and process of using same



Patented Oct. 27, 1953 DIAZOTYPE DEVELOPER COMPOSITION CONTAINING A POTASSIUM BORATE AND PROCESS OF USING SAME Franciscus Antonius Hubertus Kesscls, Venlo, Netherlands, assignor to Chemischc Fabriek L. van der Grinten N. V., Venlo, Netherlands No Drawing. Application January 14, 1953, Se-

rial No. 331,319. In the Netherlands July 14,

15 Claims.

This invention relates to a process for developing one-component positive diazotype materials and to a water-soluble developer composition adapted for use in this process.

There are two kinds of diazotype paper in use. In one type, the diazo compound and the coupling component are applied to the paper in the presence of a substance which inhibits the coupling reaction until contact of the paper with a third substance, such as ammonia, after the paper has been exposed to ultraviolet light. These are called two-component papers.

In the second type of paper, only the diazo compound is applied to the diazo paper, and these are therefore called one-component papers. The coupling component is dissolved in an aqueous solution to form a developer solution, and this is brought into reactive contact with the diazo compound on the paper to develop the latent image.

As is well known, often these developers contain an alkaline-reacting substance to bring about the coupling reaction between the diazo compound on the paper and an azo coupling component present in the developer, which results in the formation of an azo dyestuff. The alkalinereacting substance brings about the reaction by neutralizing the acid present on the paper or formed in the course of the coupling reaction, and thereby maintains a pH environment favorable to the reaction. It is also necessary that the alkaline-reacting substance be sufilciently alkaline or be present in a sufficient concentration to overcome the acidity of many developer components such as phenols.

The alkaline-reacting substances employed for this purpose are quite limited in the concentrations to which they may be brought in aqueous solutions Without introducing other difliculties. Carbonates and bicarbonates tend to produce a print whose background will discolor on storage, even in the absence of light.

Borax also has been used in developer compositions, an alkaline-reacting substance. However. borax alkalinity is so low that high concentrations of borax are required to prepare solutions of sufiicient developing strength. At the high concentrations required, crystallization of borax from the developer solution is a major problem. Crusts and precipitates of borax which form obstruct the applicator trough or the liquid applying devices of the developing apparatus. If the developer solution contacts the diazotype paper in a film, as is the case in many types of commercial equipment, the crystallization problem becomes even more acute. For this reason, borax has not been used as the principal alkaline-reacting substance of developer compositions.

Sodium metaborate is more strongly alkaline 2 than borax. It is also more soluble in water. Yet when sodium metaborate is employed in the concentrations required crystallization again is a problem, even though a sufilcient alkalinity is maintained in the developer solution, and even though the concentrations required are much smaller than the maximum solubility of sodium metaborate in water at the same temperature. As is well known, in aqueous solution borates lo exist in a complex equilibrium among the various types of borate ions. Due to this equilibrium, evidently sodium metaborate in the developer solution undergoes a transformation which yields less soluble sodium borates. These precipitate as 16 they are formed and create the crystallization problem noted.

In prior copending patent applications Serial Nos. 38,759, 229,881 (now abandoned) and 229,882 (now abandoned) filed July 14, 1948, and June 4;, 3.951, respectively, of which this application is a continuation-in-part, borate-containing developer compositions are described and claimed in which crystallization problems are overcome by including a polyhydric alcohol therein. In the as presence of the polyhydric alcohol, a sufficient concentration of borate can be maintained to furnish the required alkalinity without crystalliration of less soluble borates.

Copending patent application Serial No.

come the crystallization problem Without resort to a polyhydric alcohol. As is explained in that patent application, mixtures of potassium tetraborate and potassium hydroxide in the ratio of 0.3 to 2.3 parts potassium hydroxide to each 9 parts potassium tetraborate pentahydrate and mixtures of potassium tetraborate and potassium metaborate in the ratio of l to 17 parts potassium metaborate (calculated as anhydrous) to each 9 parts potassium tetraborate pentahydrate can be used as the alkaline-reacting substance, and the developers thus obtained shown an extraordinarily valuable combination of properties. Such developers have a pH within the range from about 9 to about 10 and do not present crystallization problems even in the absence of a polyhydric alcohol, although one can be present if desired, and present will lower the pH (compared to the same compositions without alcohol) up to about 0.5 pH unit or more, depending upon the amount.

In accordance with the instant invention, it has been determined that any potassium borate or mixture thereof as the alkaline-reacting substance in the amount required to furnish alkalinity in the developer solution will not form bcrate precipitates if the pH of the developer solution lies within the range from 8.3 to 10. Although the prior application Serial No. 229,882

60 correctly notes the importance of the ratios of potassium borates to each other and to potassium hydroxide, and the mixtures disclosed therein furnish developers having a pH Within the range of 8.3 to 10, it is the pH of the developer solution that is controlling. Accordingly, the amount of potassium borate or mixture thereof will be sufficient to furnish a developer having a pH within the range of 8.3 to 10, and potassium hydroxide will be added if necessary to adjust the pH to within this range. For achieving the advantages which a developer containing a borate can give, the concentration of the borate in the developer solution should not be less than 0.16 mol B203 per litre. On the other hand, of course, the concentration of the borate in the developer solution should not be too high to prevent crystallization and over-development; the upper limit of the said concentration should'not surpass 0.6 mol B203 per litre.

It will of course be understood that while developers can be prepared without a polyhydric alcohol which have a pH within the range of about 9 to about 10, with the addition of the polyhydric alcohol the pH can be lowered to within the range from 8.3 to 9.5.

As the pH of solutions of the developer of the invention increases towards the upper limit of 10, background discoloration tends to increase. At a pH above 10 discoloration is too severe to be tolerated. At pH values below 8.3, it becomes very difiicult to obtain complete print development.

It is theorized that above the pH value of 8.3 the borate equilibrium in the case of potassium borates causes the existence of borates of such high solubility that enough borate can be brought into solution to effect good development without crystallization. This behavior of the potassium borates is contrary to that of the sodium borates' which do not display this phenomenon, crystallizing obj ectionably at pH values within this range when present in the amount necessary to give good development.

The polyhydric alcohol functions as a supplemental pI-I adjuster, for it tends to make the solution less alkaline, possibly due to formation of a complex with the borate. The alcohol is an optional ingredient of the developers of the invention, and can be added or omitted, as desired. A reason for adding it could be to lower the pH. Any of the polyhydric alcohols disclosed in the prior applications Serial Nos. 38,759, 229,881 and 229,882 can be employed.

Other components of the developer of the invention may have an effect upon pH. Phenolic coupling components are usually acidic, for example. This will have to be taken into account in computing the amount of potassium borate or hydroxide required since some borate or hydroxide will then be taken up in overcoming the acidity of such components.

Accordingly, the developer compositions. of the invention comprise a potassium borate in conjunction with an azov coupling compound, and desirably, an antioxidant for the coupling component, and these compositions can contain a polyhydric alcohol, if desired, but are free from appreciable quantities of sodium compounds.

It will be appreciated that any potassium borate can be used, such as the metaborate and tetraborate. The pH of the solution produced will vary not only with the amount of borate, but also with the particular borate employed as a starting material. Adjustment of the pH of the developer solution to within the pH range stated 4 is best obtained by using a mixture of potassium metaborate and potassium tetraborate, or a mixture of potassium tetraborate and potassium hydroxide.

The potassium borates, including the metaborate and tetraborate, are referred to generically in the specification and claims as potassium borate,

A satisfactory developing action can also be obtained by using a mixture of a potassium borate with other water-soluble potassium salts. However, the potassium borate is always employed in the developer composition of the invention as the principal alkaline-reacting substance, and it is preferred that all of the alkaline-reacting substance be potassium borate, in view of the superior properties as regards background discoloration during storage of the prints developed with such a developer solution, which discoloration is less objectionable when only a borate is used. If under certain circumstances it is necessary to employ other alkaline-reacting substances in place of up to 50% of the borate, either for economic reasons, or when the borate is in short supply, substitute alkaline-reacting materials which can be used include carbonates, thiosulfates, phosphates, acetates and benzoates.

The azo coupling component of the developer of the invention is a substance capable of reacting with the diazonium group of the d-iazo compound on the paper to produce a dye. Such substances are well known to the art and include, for example, phenols, such as resorcinol and phlorog-lucinol, which couple with diazonium salts to form azo dyes, and similar substances, such as acetoacetanilide, 1-pheny1-3-methyl-5- pyrazolone and the like pyrazolones. The coupling component will ordinarily be selected with View to the color of the dye produced by the reaction. Resorcinol and phloroglucinol together and phloroglucinol and acetoacetanilide together, when coupled with para N-disubstituted benzene diazonium chlorides, give dark shades, while acetoacetanilide gives yellow shades, and 1-phenyl-3-methyl pyrazolone gives reddish shades. The coupling component is employed in an amount to provide from about 0.5 to about 3% by weight in the developer solution, 1% giving the optimum results.

In addition to the coupling component, when the coupling component is a phenol, it is important in order to obtain the optimum results in accordance with the invention to'include an antioxidant in amount up to about 0.1% by weight of the composition. Satisfactory antioxidants are hydroquinonemonoand disulfonic acid compounds, i. e. the free acid or its salts. The sodium salts can be used in this instance because of the smaller quantities of antioxidant used in relation to the borate. A mixture of antioxidants is usually preferable since antioxidants vary somewhat in their action and a mixture of different antioxidants gives a composition of greater stability. The composition may also include a print stabilizer, such as thiourea, and a Wetting agent such as a salt of isopropyl naphthalene sulfonic acid. Thiosulfates, such as potassium thiosulfate, can be added.

The developer composition of the invention may be prepared in solid powder form or in solution. The powdered developer is preferred for customer convenience and ease of handling. Moreover, the powdered composition is more stable. The components may be mixed together, butit is preferable to keep the borate and other in Water.

alkaline-reacting substances separate from the coupling component. As illustrated in the examples, the powdered developer can be kept in a container having two or more compartments, the borate being placed in one compartment and the coupling component in another. When the coupling component is a phenol, an anti-oxidant usually is incorporated in the compartment therewith.

All of the ingredients are reduced to a fine powder prior to packaging in order to increase the speed at which the composition dissolves The amount of the components are so chosen that the aqueous solution thereof will have a pH in the proper range, as set forth above. Usually the consumer will dissolve the developer components together or separately in a prescribed amount of water, but the amount of Water used with a given quantity of developer powder may be varied within wide limits without materially varying the pH of the solution obtainable therefrom.

The developer may also be prepared and marketed as an aqueous solution. The solution is made up simply by dissolving the components of the developer in any order in amounts to produce a solution having the desired pH.

The diazotype papers of the one-component type with which the developer composition of the invention is to be employed are well known and the following brief disclosure is a sufficient description thereof for those skilled in the art.

Many one-component diazotype papers of commerce are impregnated with an aqueous solution of a diazonium compound of the followin general formula:

where n is a number from 1 to 4, Y is selected from the group of hydrogen, alkyl, such as methyl, or halogen, such as chlorine, X is an anion, such as sulfate, or halogen, such as chlorine or bromine, R, is selected from the group consisting of hydrogen, alkyl, aryl and alkylaryl groups, and R is selected from the group consisting of alkyl, aryl, and alkylaryl groups. The alkyl group may have from 1 to l carbon atoms, such as methyl, ethyl propyl, and butyl, and may have a straight or branched chain. The alkylaryl group may have an alkyl radical of from 1 to 4 carbon atoms and be attached to the amino nitrogen through the alkyl radical, such as benzyl. The aryl group may be any monoof polynuclear aromatic ring, such as phenyl or diphenyl. The aryl group, whether alone or 'as part of an alkylaryl radical, may contain additional substituents which do not react with the diazonium group, such as additional alkyl chains, halogen, such as chlorine, etc. Preferably, R and R are selected from the group consisting of alkyl and alkylaryl groups. Typical compounds are, for example, p-(N-ethyl benzyl) amino benzene diazonium chloride p-(N-diethyl)-amino-m-chloro benzene diazonium chloride.

The diazonium group of these compounds is reactive with certain aromatic substances, such as phenols, such as phloroglucinol and resorcinol,

anilides, such as acetoacetic anilide, and pyrazolones, such as phenyl methyl pyrazolone, to pro duce a dye.

The diazotype papers available in commerce, in addition to the diazo compound, also contain a stabilizer which inhibits decomposition of the diazonium compound. Acidic stabilizers, such as organic acids, 1. e. citric, benzoic, oxalic and tartaric acids, as well as inorganic acids, such as boric acid, or acidic salts of these acids, such as aluminum sulfate, ammonium sulfate, ammonium citrate, sodium oxalate, and potassium tartrate, are usually present. An antioxidant may also be present.

The following examples illustrate preferred embodiments of the developer composition.

Example 1 The following powdered developer composition is prepared, the components being kept separate in two bags of aluminum foil:

In has No. 1:

55.0 parts potassium tetraborate pentahydrate 2.8 parts potassium hydroxide In bag ,No. 2:

4.5 parts phloroglucinol 3.85 parts resorcinol 8.5 parts thiourea 0.6 part hydroquinone monosulfonic acid potassium salt 0.5 part sodium salt of isopropyl naphthalene sulfonic acid A developer composition is prepared as set forth in Example 1, the components in bag No. 2 being the same, but the components in bag No. 1 being as follows:

47.0 parts potassium tetraborate pentahydrate 8.2 parts potassium metaborate This developer, when dissolved in 900 parts of water, gives a solution having a pH of 9.3, useful in developing the diazotype paper described in Example 1.

Example 3 Example 1 is repeated, the components in bag No. 2 being the same, but the components in bag No. 1 being as follows:

45.0 parts potassium tetraborate pentahydrate 7.45 parts potassium hydroxide (85%) This developer, when dissolved in 900 parts of water, gives a solution having a pH of 9.6. This solution can be used in developing the diazotype paper set forth in Example 1.

Example 4 The developer of Example 1 is prepared, the component in bag No. 2 being the same, but the components of bag No. 1 being as follows:

42.0 parts potassium tetraborate pentahydrate 8.2 parts potassium hydroxide (85%) This developer, when dissolved in 900 parts of water, gives a solution having a pH of 9.6 which 7 is. useful. in developing the diazotype paper described in Example 1.

Example The developer of Example 1 is prepared, the components of bag No. 2 being the same, but the components: of bag No. 1 being as follows:

30.0 parts of potassium tetraborate pentahydrate 4.0 parts potassium hydroxide (85%) This developer, when dissolved in 900 parts of water, gives a solution. having. a pH of 9.3,, which is. useful in developing the diazotype paper described in Example 1.

Example 6 The following are examples of developer solutions of the prior art. containing borax. The proportions given are of the solids. content. The remainder is. water.

The following is an example, of a developer in accordance with the instant invention;

0.49% phloroglucinol 0.34% resorcinol 0.078 hydroquinone monosulfonic acid potassium salt sodium salt of isopropyl naphthalene sulfonic acid 1.03% thiourea 6.64% potassium tetraborate -5 H2O 0.34% potassium hydroxide (85%) These developer solutions were tested on a r paper sensitized with a mixture of para (N- ethylbenzyl) diazonium chloride-zinc chloride double salt, citric acid, ammonium citrate and thiourea. Solutions, A, B, and C gave very poor development and would be considered useless under present commercial standards. Solution D gave excellent results and the prints showed good stability against accelerated light ageing and storage discoloration tests.

Ewample 7 This example contrasts the properties of developer solutions employing potassium borates and borax, respectively, as the principal alkaline.- reacting material.

0.49% phloroglucinol 0.34% resorcinol 0.078% hydroquinone monosulfonic acid potassium salt 0.06% sodium salt of isopropyl naphthalene sulfonic acid 1.03% thiourea To 794 g. of the above developer solution which, it will be noted, does not contain any alkaline reacting substance, the following amounts. of alkaline reacting substancesjwere added. toproduce four developer solutions:-

g. potassium tetraborate -5 H2O 2.8 g.. potassium hydroxide (85%) The above amount of alkali, when dissolved in the developer solution, is equivalent to: the following:

6.45% potassium tetraborate -5 H2O 0.328% potassium hydroxide (85%) The resulting developerv solution hada. pH of 9.3.

B. 20.7 g. (2.5%) borax- This solution had a pH of 8.8.

41.5 g. (5.0%) borax.

This solution had a pH of 8.9.

56 g. (6.59%) borax This solution had a pH of 90.

Each of these solutions. was employed: todevelop the paper described in Example 6. Developer solution A gave. the best development, developer solution B was unusable. because of the weak line produced while developer solutions C and D were fair, 1'. e. not quite as good asdeveloper solution A. From these results it can be concluded that borax developers containing only the amounts of borax employed in developer solutions C and D would give satisfactoryresults.

Each of the above developer solutions was then tested for performance to determine how long tallized on the rolls within 4 to 5. hours.

it would perform in a conventional developing unit without crystallization. on the rolls.

In a smooth roll unit the following results were obtained: Solution D crystallized on the rolls within 1 to 1% hours. Solution C crystallized on the rolls within 6 to 7 hours. Solutions A and B had not crystallized on the rolls at the end of 5- days.

In a multiple roll machine the following results were obtained: Solution D' crystallized on the rolls within of an hour. Solution C. crys- Solutions A and B crystallized after 2 days.

The above crystallization data show that borax developer solutions C and D are useless in modern. high speed machines. When similar amountsof borax are employed as in solution B, crystallization does not occur but the dye line is too. weak and thus such solutions are not usable. Solution A containing potassium borate gave good development without crystallization, and therefore is superior to borax developers.

The developers according to the invention exhibit attractive properties in practice, particular ly with regard to the difficulties caused by crystallization and redissolving of precipitated crystals, precipitates caused when hard water is used in the making up of the developer solutions and the like. Compared with developers containing other alkaline-reacting materials, such as carbonate developers, developers according to the invention containing a major proportion of borate as the alkaline-reacting material, show, amongst 9 said that they hardly attack the sizing of the diazotype papers used. They also possess a high ability to produce uniform prints of strong contrast or intensity.

Obvious modifications of the various aspects of the invention will occur to those skilled in the art.

All parts and percentages of developer compositions are by weight of the dry developer composition and all parts and percentages of developer solutions are by weight of the solution.

The expression consisting essentially of as used herein is intended to mean that the ingredients recited are the essential ingredients, and such expression is not intended to exclude from the composition other amounts as would not render the composition unsuitable as a developer, such as a polyhydric alcohol. Amounts of sodium compounds which would furnish a sufiicient sodium ion concentration to result in the precipitation of sodium borates are excluded by this term, but not the presence of very small quantities of sodium compounds such as would be present were a sodium compound of the antioxidant or wetting agent employed in the developer. Thus, for example, the expression excludes the use of large quantities of sodium compounds as a supplemental alkaline-reacting substance in accordance with the invention.

I claim:

1. A developer for one-component diazotype material consisting essentially of an azo coupling component and a potassium borate as the principal alkaline-reacting substance, said developer having a solution pH within the range from 8.3 to 10.

2. A developer for one-component diazotype material consisting essentially of an azo coupling component, a potassium borate as the principal alkaline-reacting substance, and a substance selected from the group consisting oi? hydroquinone sulfonic acid and salts thereof, said developer having a solution pH within the range from 3.3 to 10.

3. A devoloper for one-component diazotype material which is entirely soluble in an aqueous developing medium at a concentration effective to develop the material when applied as a thin liquid film and which consists essentially of an azo coupling component and a potassium borate as the principal alkaline-reacting substance, said developer having a solution pH within the range from 8.3 to 10.

4. A developer for diazotype material consist-- ing essentially of an azo coupling component and potassium tetraborate as the principal alkaline-reacting substance, said developer having a solution pH within the range from 8.3 to 10.

5. A developer for diazotype material consisting essentially of an azo coupling component and potassium tetraborate and potassium metaborate as the principal alkaline-reacting substances, said developer having a solution pH within the range from 8.3 to 10.

6. A developer for diazotype material consisting essentially of an azo coupling component, and potassium tetraborate and potassium hydroxide as the principal alkaline-reacting substances, said developer having a solution pH within the range from 8.3 to 10.

ingredients in such 7. A developer for one-component diazotype material consisting essentially of an azo coupling component, an antioxidant, and. a potassium borate as the principal alkaline-reacting substance, said developer having a solution pH within the range from 8.3 to 10.

8. A developer in accordance with claim 7 in which the borate consists essentially of a mixture of potassium metaborate and tetraborate.

9. A developer in accordance with claim 7 in which the borate consists essentially of a mixture of potassium tetraborate and potassium hydroxide.

10. A developer in accordance with claim 7 in which the azo coupling component is a mixture of phloroglucinol and resorcinol.

11. A developer in accordance with claim 7 in which the azo coupling component is a mixture of phloroglucinol and acetoacetanilide,

12. A developer in accordance with claim 7 in which the antioxidant is a potassium salt of hydroquinone sulfonic acid.

13. A packaged water-soluble developer in powder form for one-component diazotype material composed of a plurality of portions, one portion consisting essentially of a potassium borate as the principal alkaline-reacting substance, and another portion consisting essentially of an azo coupling component, said (leveloper having a solution pH within the range from 8.3 to 10.

14. A packaged water-soluble developer in powder form for one-component diazotype material composed of a plurality of portions, one

' portion consisting essentially of an azo coupling component and an antioxidant, and another portion consisting essentially of a potassium borate as the principal alkaline-reacting substance, said developer having a solution pH within the range from 8.3 to 10.

15. A process of producing positive diazotype prints from one-component diazotype material which comprises contacting under reaction conditions a one-component diazotype paper comprising a diazonium salt with an aqueous developer solution consisting essentially of a compound capable of coupling with the diazonium compound to produce a dye, an antioxidant, and a potassium borate as the principal alkalinereacting substance, said developer having a solution pH within the range from 8.3 to 10.

FRANCISCUS AN TONIUS HUBERTUS KESSELS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,816,989 Schmidt et al. Aug. 4, 1931 1,837,679 Schmidt et al. Dec. 22, 1931 1,989,065 Schmidt et a1. Jan. 22, 1935 2,037,542 Schmidt et al. Apr. 14, 1936 2,063,832 Werner Dec. 8, 1936 2,091,689 Russell Aug. 31, 1937 2,151,532 Schmidt et al. Mar. 21, 1939 2,239,704 DeBoer et al. Apr. 29, 1941 2,241,104 Van Der Grinten May 6, 1941 FOREIGN PATENTS Number Country Date 320,603 Great Britain Oct. 14, 1929 403,203 Great Britain Dec. 21, 1933 

1. A DEVELOPER FOR ONE-COMPONENT DIAZOTYPE MATERIAL CONSISTING ESSENTIALLY OF AN AZO COUPLING COMPONENT AND A POTASSIUM BORATE AS THE PRINCIPAL ALKALINE-REACTING SUBSTANCE, SAID DEVELOPER HAVING A SOLUTION PH WITHIN THE RANGE FROM 8.3 TO
 10. 